Researchers at University College London found that as more people used e-cigarettes, more people successfully quit smoking – but warned that firm conclusions about cause and effect could not be drawn.

Data was collected from more than 170,000 smokers aged 16 and over taking part in the Smoking Toolkit Study.

Researchers used a time series analysis to look at the relation between changes in e-cigarette use and prevalence of quit attempts, success of those attempts and the use of prescribed medicine and behavioural support services.

The researchers said that the results ‘conflict[ed] with the hypothesis that an increase in population use of e-cigarettes undermines quitting in general.’

E-cigarette use among people trying to quit smoking was found to be negatively associated with nicotine replacement therapy on prescription, according to the researchers

Cancer Research UK welcomed the findings but said that prescription medication and smoking cessation services remain the most effective way to quit smoking.

Alison Cox, director of prevention at Cancer Research UK said: ‘It’s important to remember that getting support from Stop Smoking Services is still the most effective way to quit.

’We’ll continue to fund research into e-cigarettes to build our understanding, and encourage people to combine the most popular method with the most effective – Stop Smoking Services. But this study reassures us of the promise these products have.’

The Department of Health and PHE recently backed use of licensed E-cigarettes to help people give up smoking, as an alternative to other nicotine-replacement products.

A 200-page report from the Royal College of Physicians published earlier this year found that E-cigarettes encourage people to quit smoking and do not act as a gateway to smoking for adults or children.